The use of hydraulic actuators, for example in aircraft, is well established. For example, they are used for flight control applications such as moving control flaps, for landing gear extension and retraction, and so on.
Conventionally, a plurality of actuators are coupled to a common hydraulic circuit that comprises a reservoir and a pump. An advantage of hydraulic actuators is the ability to provide a relatively high power density.
A disadvantage of the above described arrangements is that servicing or replacement of individual actuators can be relatively complex due to the possibility of requiring to bleed, flush and replenish the whole hydraulic circuit.